Electronic Structure of Ferroelectric Material Probed by Soft-X-Ray Spectroscopy

The polarization dependence for the electronic structure of Bi₄Ti₃O₁₂ (BIT) single crystal has been studied by soft-X-ray emission spectroscopy (SXES) and X-ray absorption spectroscopy. The valence band and conduction band are mainly composed of O 2p state and Ti 3d state, respectively. The SXES spectra measured at the Ti 2p absorption edge region exhibit three structures, which correspond to elastic scattering, fluorescence and soft-X-ray Raman scattering. The Raman scattering corresponds to the charge-transfer (CT) energy, which corresponds to the transition from O 2p state to unoccupied Ti 3d state. The CT energy in the a-c plane is different from that in the a-b plane. The difference of CT energy originates to the lattice constant and hybridization effect in BIT single crystal.